Inhalers or puffers may be used for delivering medication into the body via the lungs. They can be used, for example, in the treatment of asthma and chronic obstructive pulmonary disease (COPD). Types of inhalers may include metered dose inhalers (MDIs), dry powder inhalers (DPIs) and nebulizers.
A common problem faced in respiratory drug delivery is how to monitor patient adherence and compliance. Adherence deals with the patient following the prescription label, for example taking the prescribed number of doses per day. For example, if the prescription calls for two doses each day, and the patient is taking two doses a day, they are considered 100% adherent. If the patient is only taking one dose a day, they are only 50% adherent. In the latter case, the patient is not getting the treatment prescribed by their doctor.
Compliance, on the other hand, relates to how the patient uses their drug delivery device. If used in the manner recommended for effective treatment, they are 100% compliant. If not used properly however, they are less than 100% compliant. Use of a breath-actuated inhaler (e.g., a dry powder inhaler (DPI)) involves inhaling in a particular way; for example the inhalation may need to be long enough and hard enough to entrain a full dose of medicament. For some patients, for example children and the elderly, meeting the requirements for full compliance may be difficult. Failing to achieve 100% compliance can reduce the effectiveness of the prescribed medicament.
It is difficult for a patient to determine whether he or she inhaled the prescribed dose of medication and thus to verify compliance with the prescription. Especially for DPIs, a patient may not immediately notice that medication is being inhaled (e.g., because the particles are so small they may not be felt or tasted). A patient may learn of inhalation after seeing the medical effects and still may not know whether the amount of inhaled medication complies with the prescription.